I guess the 12 count is either "un-00" a little smaller or it is the 3 inch...
I am not wanting to increase the recoil more than I must so I use the 9 count shell. I do live in a split plan so I just have to make dang sure my payload is slowed by a torso before hitting a wall...
Nothing mitigates the risk of over penetration like a squishy BG torso...
Brent